In general, dressings to be applied to various types of wounds, including burns and the like, should ideally promote healing, and provide protection, e.g. a bacterial barrier against infection, and prevent pooling of wound exudate. While of lesser importance, they should also be as comfortable as possible and not cause or contribute to ancillary problems such as bed sores and the like which are common with patients bedridden for extended periods of time following surgery or treatment for burns and/or inflicted wounds. Moreover, they should ideally be transparent for visualization and monitoring of the underlying wound.
For convenience, such products will be referred hereinafter throughout the specification and claims simply as "wound dressings".
While wound dressings are known in the art which will provide some of the above-noted desired properties, prior to the present invention the need for an improved wound dressing more closely approximating the above criteria still exists.
For example, the patent literature is replete with references to various types of wound dressings, including dressings employing hydrogel layers to absorb wound exudate. Nevertheless, at present there are essentially only two types of wound dressings commercially available, each of which affords certain advantages but also suffers from certain disadvantages.
The first such commercially available product is a hydrogel such as "Vigilon" (trademark of C. R. Bard, Inc. for a non-adherent, breathable, moist hydrogel which is inert, 96% water and 4% polyethylene oxide.) The Vigilon hydrogel provides a moist environment conducive to wound healing and granulation tissue formation as well as the absorption of wound exudate which should be inherent in the function of hydrogels in general. However, it is not highly absorbent and consequently requires fairly frequent replacement to obviate pooling of exudate and related problems. Moreover, since it is non-adherent to intact skin, it requires use of adhesive tape for application to the skin as well as applying gauze or other covering means to prevent escape of the exudate. Apart from the time, trouble and expense of storing and assembling the materials needed to complete the wound dressing, bulky bandages frequently result, particularly where the wound covers a large or irregular surface. This in turn may contribute to the further discomfort of the patient as well as bedsores from the chafing and rubbing. Hydrogels such as Vigilon are disclosed, for example, in U.S. Pat. Nos. 3,419,006; 3,664,343; and 3,993,551.
For these and perhaps other reasons, a more commonly used product for wound dressings is "DuoDERM" (trademark of E. R. Squibb & Sons, Inc. for a dressing containing moisture reactive particles surrounded by an inert, hydrophobic polymer.) The DuoDERM dressing has an adhesive inner surface for application to the skin and wound and is said to be virtually impermeable to oxygen. As moisture enters the dressing, the moisture-reactive particles gradually swell and dissolve to contain the accumulating exudate.
Wound dressings of the DuoDERM structure afford certain advantages, chief of which are the fact they are unitary structures including the adhesive layer for securing the dressing, ease of application and the ability to contain exudate.
However, they possess certain significant disadvantages as well, e.g. the adhesive layer is a barrier to diffusion of exudate from the wound so that most of the fluid never diffuses through the adhesive layer; no transpiration of fluid through the impermeable outer surface; the adhesive is aggressive to the intact perilesional skin so that on removal this skin may be traumatized; loss of adhesion in a day or two due to fluid accumulation; tendency to exhibiting an unpleasant odor when dissolved in wound fluid; and the oxygen-free environment provided by the oxygen- and water-impermeable outer surface provides a favorable environment at the wound locus for the growth of harmful anaerobic bacteria.
The above two products are, in applicant's judgement, fairly representative of commercially available wound dressings. Others of course do exist.
It is also known in the art to employ collagen in wound dressings. Illustrative patents pertaining thereto will be discussed subsequently in the "Detailed Description of the Invention".
In general, it can be said that it has long been known that some types and/or forms of collagen promote wound healing and may accordingly be employed in wound dressings. However, they lack the absorbency capacity of hydrogels and, apparently for this reason, are not known to be employed in commercially available wound dressings.
As previously stated, the patent literature contains numerous references to wound dressings, particularly dressings employing hydrogels.
While not intended to be a complete survey of the state of the art pertaining thereto, the following additional patents are nevertheless illustrative: 3,249,109; 4,153,055; 4,347,841; 4,367,732; 4,438,258; 4,516,571; 4,541,426; 4,552,138; and 4,556,056.
As was also previously stated, a wound dressing should ideally promote healing, provide protection against infection, minimize pooling of wound exudate yet allow subsequent aspiration, be as comfortable as possible and not contribute to wound trauma on removal, etc. Moreover, they should preferably be easy to apply. At present, there are no available wound dressings providing all of the above functions.
The task of the present invention may accordingly be said to be to provide a wound dressing which satisfies the above-mentioned criteria in a composite structure which is both easy to apply and also contains all of the components essential for application and retention of the dressing to the skin.